The present invention relates to an encoding and decoding device for error-detecting data transmission systems, in particular for remote-control and remote-actuation equipments.
Known error-detecting methods operate, for example, with fixed particles of the data words, to make the detection of an error possible. With such a system, errors are detected to a large extent. However, the detection cannot be considered satisfactory in all cases since, with an invalidation at the same time of two bits of a given data word, the right parity is restored even though the data word has been invalidated. Particularly in radio transmission devices, such a disturbance cannot be eliminated.
In other known methods, every data word is transmitted two times in sequence and the first word is stored separately, in parallel, and compared with the subsequent word. Differences are evaluated as errors. Known circuits have the disadvantage that periodic disturbances may invalidate the two values in the same manner so that no error can be detected. Further, the parallel-connection technique used in these circuits does not appear as an optimum solution for the MOS technique and integrated circuits.
According to other methods known in the wire transmission of information, the data are transmitted in parallel over two lines, with one line transmitting the positive-going data values and the other line transmitting the inverted values. A coincidence of the two transmissions is the error criterion. This method is tied to two parallel transmission paths and, therefore, frequently unusable.